Registry To Change DefaultIcon For File Types

1) How can I change the default icons for file types in the registry? I added the key "DefaultIcon" to several file types as listed in HKEY_CLASSES_ROOT and set the data to the full file path of the icon I'd have thought that would work. I've restarted, and it did not.Where is the correct location & method?

2) Also: (once I get the correct location & make the edits) How can I create a registry file that will add the specified changes to an existing registry when clicked? Not save the entire registry, and replace it, just add the specified keys & data to install these icon changes. This should be at least good as a backup, for editing a new or reinstalled OS, and ideally (if possible) a file that can perform a smart operation by substituting or getting around the current system's user folder name.